1. Field of the Invention
The present invention relates to occupancy and vacancy sensors for detecting an occupancy or a vacancy in a space, and more particularly, to a wireless load control system including a plurality of battery-powered occupancy or vacancy sensors for detecting an occupancy or a vacancy in a space, and a load control device for controlling the amount of power delivered to an electrical load in response to the occupancy or vacancy sensors.
2. Description of the Related Art
Occupancy and vacancy sensors are often used to detect occupancy and/or vacancy conditions in a space in order to control an electrical load, such as, for example, a lighting load. An occupancy sensor typically operates to turn on the lighting load when the occupancy sensor detects the presence of a user in the space (i.e., an occupancy event) and then to turn off the lighting load when the occupancy sensor detects that the user has left the space (i.e., a vacancy event). A vacancy sensor only operates to turn off the lighting load when the vacancy sensor detects a vacancy in the space. Therefore, when using a vacancy sensor, the lighting load must be turned on manually (e.g., in response to a manual actuation of a control actuator).
Occupancy and vacancy sensors have often been provided in wall-mounted load control devices that are coupled between an alternating-current (AC) power source and an electrical load for control of the amount of power delivered to the electrical load. Such wall-mounted load control devices typically comprise internal detectors, such as, for example, a pyroelectric infrared (PIR) detector, and a lens for directing energy to the PIR detector for detecting the presence of the user in the space. With a PIR detector, motion is detected when an infrared source having a first temperature passes in front of an infrared source having a second temperature. Since the wall-mounted load control devices are mounted to a wall in a standard electrical wallbox (i.e., replacing a standard light switch), the detection of energy by the PIR detector may be hindered due to the direction that the load control device is facing and by obstacles in the space, thus increasing the likelihood that the load control device may not detect the presence of a user.
Some prior art occupancy and vacancy sensors have been provided as part of lighting control systems. These sensors are typically coupled via a wired control link to a lighting controller (e.g., a central processor), which then controls the lighting loads accordingly. Since the control link is typically a low-voltage control link, these occupancy and vacancy sensors are not required to be mounted in electrical wallboxes, but may be mounted to the ceiling or high on a wall. Therefore, the occupancy and vacancy sensors may be positioned optimally to detect the presence of the user in all areas of the space. However, these prior art lighting control systems require advanced system components and configuration procedures in order to operate properly.
Thus, there is a need for a simple lighting control system that has occupancy or vacancy sensors which may be easily and optimally installed into a space.